[DOCS] Add documentation for boolean operations

[navasvarela]

**What section of the docs could be improved? **
Nada Lang operators

What part(s) of the docs would you like to see updated?
We need to add documentation for the boolean and, or, not operators. see https://github.com/NillionNetwork/nillion/pull/2084

Additional context
We might also want to update nada by example with example programs.

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